She is the glamorous other half of a political couple who have been dubbed Germany's answer to the Kennedys, admired for their sparkling public appearances and aristocratic backgrounds and said to be the nearest thing Germany has to royalty.

But Stephanie zu Guttenberg, great granddaughter of the founder of the German empire, Otto von Bismarck, and the wife of Germany's defence minister, Karl-Theodor zu Guttenburg, is finding her rising star overshadowed by pressure to distance herself from a TV show in which she helps expose alleged paedophiles.

Zu Guttenberg, whose celebrity has been growing as rapidly as that of her charismatic 38-year-old husband, co-presents Tatort Internet. The show involves an actor, impersonating a teenager, who communicates via web chat rooms with men searching for sex with minors. When a man meets the "girl" he is confronted by a journalist posing as her mother and the incident is secretly filmed.

The show has been compared to the US series To Catch a Predator, which was abandoned after a Texan lawyer shot himself dead during filming when he was confronted in his home by police accusing him of paedophilia.

The German programme, broadcast by the tabloid channel RTL2, has now come under fire from child protection groups, the justice minister and lawyers, after an alleged child abuser exposed by the show this month went underground. The programme makers admitted they failed to inform the police of their suspicions about the man, the 61-year-old head of a youth group funded by the Catholic charity Caritas. His family said he did not go home after being fired by the charity when the allegations were made and his identity was revealed on the web. They fear he might have taken his life.

Zu Guttenberg, 33, who is patron of the German branch of the paedophile campaign group Innocence in Danger and an advocate of child protection (last month she published a book, Don't Look Away) has abstained from commenting on what is fast becoming a political scandal.

Previously she has defended the show, and its format, which has been compared to a horror film with its shaking images and scary music, arguing that the most important aspect was the message. "RTL2 is much-watched by young families and they're the ones we want to inform."

She said she could not understand the "tendency to want to protect the perpetrators over the victims". Innocence in Danger had tried for years to get the topic on television and had one rejection after another, while RTL2 "showed a lot of courage" in making the programmes.

So far the programme makers count among their triumphs the exposure of a German soldier, 33, who allegedly tried to lure the show's "13-year-old" into a forest for sex, and a 51-year-old who went to meet her in a flat.

The tabloid Bild headlined a story on the exposures "Bravo, Stephanie zu Guttenberg!" Child protection charities have called the show's tactics "outrageous", "manipulative" and damaging to the cause of exposing paedophiles. They accused the makers of being interested only in ratings.

Today the justice minister, Sabine Leutheusser-Schnarrenberger, said the show was in danger of operating above the law as it named and shamed before people could defend themselves. "There is the danger that innocents will be put in the stocks and damage caused, and the rule of law will be thrown out of balance," she said.